The present invention relates to a vibrating microdevice, such as a vibrating micromirror.
Vibrating micromirrors, which are manufactured using surface micromechanics and have a variety of forms of springs and suspensions, are conventional. For example, German Published Patent Application No. 198 57 946 describes micro vibrating mirrors, which are used in sensing the passenger compartment of motor vehicles, in scanning, or for laser deflection.
Conventional vibrating micromirrors (e.g., those manufactured from silicon with the aid of micro-mechanical methods) are only be operated at relatively small operating or torsion angles. In order to attain operation at large torsion angles, springs, from which the actual mirror surface is suspended from a supporting body in a largely floating manner, must be designed to be very thin, since only relatively small driving forces (e.g., forces for inducing a torsional vibration) are available.
However, in the case of the mirror surfaces being relatively large in comparison to the spring thickness, externally applied forces, which, e.g., occur in response to a bump or collision, occasionally result in the destruction of the springs by breaking or tearing.
It is an object of the present invention to provide improved springs of a vibrating microdevice, in particular a vibrating micromirror. In this context, the springs may connect the actual vibrating surface to a supporting body in a largely floating manner, allow a torsional vibration of the vibrating surface, and absorb and deflect forces (e.g., external forces) that act suddenly and are directed at least partially perpendicularly to the vibrating surface, so that the springs are prevented from breaking.
The vibrating microdevice according to the present invention includes spring structures that reduce the mechanical workload of the actual torsion-spring elements, especially with regard to bending stresses. This arrangement allows the torsion-spring elements to be designed thinner, which permits the use of smaller forces to induce a torsional vibration of the vibrating structure. In addition, a longer travel (i.e., greater torsion angle) may be achieved by these forces. Furthermore, the vibrating microdevice of the present invention reduces the load on the torsion-spring elements during the manufacturing process, which results in fewer losses during production.
In addition, the thin torsion-spring elements, in connection with the smaller applied forces for inducing the torsional vibration, may reduce the outlay for electronically controlling the vibrating microdevice. At the same time, the increased robustness of the vibrating microdevice according to the present invention also allows manufacturing tolerances to be reduced during the manufacturing process, so that simpler and more cost-effective manufacturing methods may be used.
In addition, the vibrating microdevice of the present invention remains robust in the case of mobile use, while simultaneously being constructed simply and having less outlay for connection techniques, which leads to cost savings.
Further, production of the microdevice according to the present invention does not require new manufacturing methods. The device may be produced completely by conventional technologies. Moreover, additionally provided converter structures may be produced in the same method step as the production of the vibrating structure and the torsion-spring elements.
The greatest mechanical load on the spring structure of the vibrating microdevice according to the present invention generally occurs in response to a sudden impact. In this context, the impact energy and the impact momentum are mainly transmitted to the vibrating structure. The vibrating microdevice and an employed converter structure of the present invention may absorb the energy stored in the movement of the vibrating structure through elastic deformation of the spring structure. Particularly, the converter structure damps the transmitted momentum, which results in the torsion-spring elements being largely subjected only to tensile stresses, which are directed essentially parallel to the torsion axis of the torsion-spring elements. These tensile stresses are uncritical and rarely lead to tears or breaks of the spring structures. Undesirable bending stresses, which frequently cause conventional torsion-spring elements to break, may be absorbed by the converter structure, partially damped, and at least partially converted to uncritical tensile or compressive stresses.
The vibrating microdevice of the present invention is capable of absorbing and tolerating markedly greater forces, including those of short duration, since the torsion of the converter structures considerably lowers the bending stress of the torsion-spring elements, especially at the transition or connection points, the critical tensile stress for the torsion-spring elements being markedly greater than the critical bending stress.
In addition, rectangular or angular transitions or structures of the converter structures or the spring structures may be rounded, resulting in a further increase in rigidity. Furthermore, the configuration of a first converter structure attached between the torsion-spring element and the supporting body may differ from that of a second converter structure attached between the torsion-spring element and the vibrating structure. Differing configurations may also be employed if a plurality of spring structures are used to connect the vibrating structure to the supporting body. The spring structures may then have different configurations as well. In this context, the term configuration includes shape of the structure, materials used, and/or material strength.
The vibrating microdevice of the present invention may also be provided with stop structures, which limit, to maximum values, a local movement of the vibrating structure from a neutral position exceeding the torsional vibration and directed parallel and/or perpendicular to the direction of the torsion axis. Consequently, the upper limits or critical maximum values of elongation or bending of the torsion-spring elements or the converter structure may be preselected, in order to prevent additional breaks or tears.
Further, the stop structures may be flexible as well, so that they are able to cushion or damp a local movement of the vibrating structure exceeding the torsional vibration, from the neutral position, parallel and/or perpendicular to the direction of the torsion axis. This provides additional protection from tearing or braking at critical loads.